1. Field of the Invention
The present invention relates to a zinc oxide-based transparent conductive film and a process for forming such a film. The zinc oxide-based film is a Ga.sub.2 O.sub.3 or In.sub.2 O.sub.3 -doped zinc oxide film having an improved conductivity.
2. Description of the Related Art
As a transparent conductive film, an ITO (Indium Tin Oxide) film is used for transparent electrodes in solar cells and electroluminescence display devices, etc. An alternative transparent conductive film of zinc oxide (ZnO)-based is also known, which material is cheap and widely available. Recently, aluminum has been added to a ZnO-based transparent conductive film to improve the resistivity of the film, and a radio frequency sputtering is usually used for forming such a ZnO-based transparent conductive film, including an Al-doped film. Nevertheless, in the above method, the substrate must be arranged perpendicular to or inclined by 45.degree. to the target, and the film must be about 300 nm thick to obtain a ZnO-based transparent conductive film having a resistivity as low as that of ITO. Accordingly, it is very difficult to obtain such a film uniformly over a large area.